1. Field of the Invention
The present invention relates to a process of making a Josephson junction device having a superconducting oxide film with a high superconducting transition temperature, and an improved Josephson junction device.
2. Description of the Invention
Josephson junction devices having superconducting elements are now regarded as high-speed elements superior to semiconductors since they can operate at increased speeds and also with reduced consumption of electric power. The trial manufacture of a Josephson computer is being energetically undertaken by many manufacturers (see "Technique of Josephson Computer", Parity, Separate Volume No. 1, 1986, pp 40-47).
Josephson junction devices presently developed are mainly of a tunnel Junction type in which a very thin film is sandwiched between members of niobium or niobium nitride. These conventional Josephson junction devices are made on the assumption that they operate at liquid helium temperature. If Josephson junction devices are formed of a superconducting oxide, they can operate at higher temperature (e.g. liquid nitrogen temperature), resulting in an increase of practicality and economical efficiency.
On the other hand, it is known in the art that the naturally produced tilt-boundary junction functions as a Josephson junction. It has been reported that the critical current was measured in a twin tilt-boundary junction of the yttrium compound (YBa.sub.2 Cu.sub.3 O.sub.7-.delta.). See "PHYSICAL REVIEW LETTERS" issued on Jul. 11, 1988, Vol. 61, No. 2, pp 219-222.
However, a method of controlling the production of a Josephson junction of the tilt-boundary junction is still not known. In the prior art, therefore, it was difficult to produce a number of such Josephson junctions having any patterns at desired locations.